Tab is not visible for single member in shared channel

Hello everyone,

Another day, another M365 mystery. I have a client who added a website tab to a shared channel that is linked to a Planner plan. Technically, this “plan” isn’t a standard plan, as it was created via a Loop component in the channel conversation. Very confusing, I know.

So far, so good—this tab is visible to all members of the shared channel except one person. I’ve checked, and everyone has the same licenses. Any ideas on how to solve this mystery?

Best regards,
Hisham